1. Field of the Invention
The present invention relates to underground junction boxes.
2. Description of the Prior Art
There are many forms of public utility and other cabling in which cables are run underground between a variety of buildings. Such cables may be, for example, power cables, telephone cables, and TV cables; in the case of signal cables, the cables may be electrical or fibre optic cables. Access to such cables is required at suitable intervals, and is generally provided by means of underground junction boxes. Such boxes have dimensions of the order of a meter, and are buried so that their upper face is flush with the ground surface. Their upper face consists of a removable plate, allowing access to the cables in the box.
Such boxes are naturally used most frequently in locations where there is a lot of traffic, foot or vehicular, and the ground surface is therefore usually metalled.
Over the course of time, such metalled surfaces become worn. The primary effect of such wear is a change of the character of the surface metalling, usually resulting in increased slipperiness. As time goes on, such surfaces also suffer localized damage, often as a result of particular parts being dug up. Such surfaces therefore require periodic resurfacing. It is very expensive to remove the existing surface, and it is therefore common for such resurfacing to consist of laying a fresh layer of metalling on top of the existing surface. This results in the level of the surface being raised.
A problem thus arises with buried junction boxes, because their top surface has to be raised to the new surface level. If the box is constructed of brick, then there will be a frame mounted on the top of the brick courses, and this frame has to be removed, the top course of bricks has to be raised (e.g. by adding a fillet of concrete round it), and the frame rebedded.
Junction boxes are often now constructed of plastic material. These present a more difficult problem when their top surface has to be raised, because the box is generally an integral structure. It is generally necessary for a separate frame to be mounted on the top of the box and for the top rim of the box to be cut off to make room for the additional frame, or alternatively for the complete box to be reinvested (that is, removed and replaced at its new level). These procedures are inconvenient and costly.
A major purpose of the present invention is to provide an improved junction box in which this problem is alleviated or overcome.
Junction boxes are required in a wide variety of situations. Thus the number of cables entering a box may vary widely, the required depth may vary (or if the cables are already be in situ, their depth may vary), the minimum bending radius of the cables may vary, the space available for accommodating the box may be constrained, and so on. Hence a single box design is not suitable for all situations; to cope with an adequate range of situations, the box size must be variable in both area and depth.
A further object of the present invention is to provide a box design principle which provides such variability with a minimum number of components.